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Aviation History
1956
1956 - 0569.PDF
11 May 1956 569 Armstrong Siddeley Viper ASV.10. Trainer turbojet. Seven-stage compressor,annular vaporizing combustion chamber and single-stage turbine. Overall diameter, 28in (basic diameter, 23.2in); overall length, about 70in; mass flow,42 Ib/sec; pressure ratio, approximately 4:1; dry weight, 570 Ib; maximum thrust, 2,000 Ib at 13,800 r.p.m. with s.f.c. of 1.01. Armstrong Siddeley Double Mamba ASMD.3. Double turboprop. Twomechanically independent power sections each driving one unit of twin co-axial airscrews; each power section is that of a Mamba ASM.5, with ten-stage compressor,annular combustion chamber and three-stage turbine. Overall width. 52.8in; height, 44.25in; length, 98.7in; dry weight, 2,2001b; mass flow (total), 37 Ib/sec;pressure ratio, 5.35:1; maximum rating, 3,035 e.n.p. (2,740 s.h.p.4-770 Ib) at 15,000 r.p.m. with s.f.c. of 0.71. This engine is cleared to run on ship's diesel fuel. already in production and other Sapphires are repoited to be still morepowerful. Although not yet placed in production, considerable development hastaken place on afterburning engines from both the original and the new Sapphire families. It is unofficially reported that the Sa.7 with after-burner is designated Sa.5. The Sapphire afterburner incorporates unusual design features such as vaporizing fuel burners. In the designof this unit Armstrong Siddeley co-operated with Dowty Fuel Systems, Ltd., who supply the ENG.181 reheat pump and ENG.224 throttle con-trol which gives rise to the supposition that the boost is infinitely variable. Development Sapphires with fixed-orifice afterburners have been flyingin Canberras for some two years and a more advanced installation is now fitted to a prototype English Electric P.I. Viper. Originally a short-life engine for the Australian Jindiviktarget, major production applications now extend to other fields including piloted aircraft, chief among which is the Jet Provost basic trainer.Early powerplants like the Viper 101 (ASV.5) were rated at 1,640 lb thrust. Later developments showed that the ASV.5 (13,400 r.p.m.) or 8(13,800 r.p.m.) could be operated at increased temperatures to permit a revised rating of 2,000 lb, but for piloted trainer applications a verylong and trouble-free life is essential, and this led to the ASV.10. Although fitting the same space-envelope as its predecessors, themass flow has been increased from 32 to 42 lb/sec at 13,400 r.p.m. At the same time the opportunity has been taken to redesign thecompressor along the lines of the latest Sapphires with blades mounted on discs carried on a central drum. Other new features are theSapphire-type combustion chamber back-plate with 24 burners and the provision for an accessory take-off from the nose (and not fromthe side as previously). Another unit is the ASV.ll which is an increased-flow Viper run at greater top temperatures and rated at2,460 lb thrust yet weighing no more than the ASV.10. Various types of Viper have also been developed with afterburners, and independentdevelopment of such powerplants is now being carried out by Dassault in France (q.v.). Production Viper ASV.3s are being exported to the U.S.A. for theJindivik programme of East Coast Aeronautics, Inc. Their import is handled by Curtiss-Wright, who are likely to licence-produce the Vipershould large Jindivik orders be placed by the U.S. services. Double Mamba. Consisting of two Mamba power sections eachcoupled to its own half of a double, co-axial airscrew unit, this unique powerplant provides high take-off power (for the Gannet search/strikeaircraft) as well as facilitating an efficient and straight-forward single- engine cruise procedure. The first production unit, designated ASMD.l,is now extensively used by the Royal Navy and R.A.N. who are well pleased with its behaviour. Production of the ASMD.l is shortly togive way to the ASMD.3, each power section of which is designated Mamba 5 and resembles the ASM.6 without the added zero-stage onthe compressor. The ASMD.3 was fully type-tested last summer. Brief mention may also be made of the ASMD.4 which broadly con-sists of a pair of Mamba 6 power sections, but introduces a completely new front-end with a lower thrust line. In view of the performance ofthe later Mambas, it appears that it should not be impossible to have a 4,000-h.p. Double Mamba in service before very long. Mamba. This name relates to a series of medium-power turbopropswhich began after World War 2 at less than 1,000 e.h.p. and now includes units delivering almost twice this amount and with outstandingefficiency. Of the present units the most important is the ASM.6, to which rating production deliveries have been made for the Seamewfor over a year. These production engines have consistently bettered the "brochure figures" quoted beneath the drawing. Compared with earlier Mambas, a zero-stage has been added to thecompressor (resulting in a longer casing). The vaporizing combustion chamber is of the truly annular variety and the turbine has a third stageadded (again increasing the casing length). Special features include a twin-breech cartridge starter, a ventral oil tank, full de-icing, an airscrewbrake and a drive for a remote accessory box. Generally similar is the civil Mamba '7 which is characterized by very low s.f.c. It can bestated that the 1,650 s.h.p. rating is by no means the ultimate, and it may be expected that later military Mambas will be yet more powerful. Python. The first large turboprop in the world to enter operational service—in the arduous duty of powering a carrier-based attack fighter Armstrong Siddaley Mamba ASM.4. Single-shaft turboprop. Eleven-stagecompressor, annular combustion chamber and three-stage turbine. Overall diameter, 33in (basic diameter, 29in); length as shown, 90.2in; dry weight, 951 Ib;mass flow, over 20 Ib/sec; pressure ratio, about 6:1; maximum rating, 1,770 e.h.p. (1,650 s.h.p. + 3201b) at 15,000 r.p.m. with s.f.c. below 0.695. —the 4,110-e.h.p. Python is no longer in production. Now highlydeveloped and quite popular with its pilots, its features include separate, reverse-flow, vaporizing combustion chambers, a torque-meter, a brake for the concentric airscrew shafts and an air, electric or cartridge starter. Rocket Motors. It is now ten years since Armstrong Siddeley Motorsbegan the development of pump-fed, liquid-oxygen aircraft rocket motors. The first project was the Snarler, a 2,000 lb-thrust engine Armstrong Siddeley Sapphire: pro- duction unit of ASSa.7 rating.
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